Diabetes 20, Diabetic Retinopathy

Microvascular disease of the retina occurs as a result of basement membrane thickening. Retinal arterioles narrow and may become completely occluded. These changes lead to hypoxia in ischaemic areas of the retina. Chronic retinal hypoxia results in the release of growth factors including a factor which stimulates the rapid generation of new blood vessels. More blood vessels could carry more blood to the area and so counter the hypoxia. However there is a problem. In the retina the excessive growth of new small blood vessels is called proliferate retinopathy. These new vessels have fragile walls which can rupture and bleed; this will cause retinal haemorrhages which cause progressive damage to the light sensitive cells. Regular retinal examination and possible photocoagulation can cauterise new vessels before they have time to haemorrhage, this can prevent or delay the development of blindness. Poor glycaemic control, with hyperglycaemia is a definite risk factor for diabetic retinopathy. From this it is clear that good levels of glycaemic control reduce the probability of this complication developing. Hypertension is another risk factor for diabetic retinopathy which should therefore be managed. Diabetics are also more prone to cataracts (opacity of the lens) and glaucoma (increased pressure within the eyeball).